The present invention relates to a method and a device for winding yarn onto a conical or frusto-conical spool body driven about its longitudinal axis onto which the yarn is placed by a reciprocating yarn guide, whereby the revolutions per minute of the spool body is synchronously changed with the movement, respectively, the respective instant placement position of the reciprocating yarn guide and as a function of the diameter of the spool body in order to affect across the length of the spool body and also during the entire winding process a substantially constant yarn winding speed onto the spool body.
Winding of yarn onto a conical spool body is a problem when it is desired to supply or remove the yarn with a constant speed. Independent of the drive action of the spool body by a friction roller or a direct driving action of the spool body, for a constant rpm of the axle of the spool within one layer of yarn, less yarn is wound onto the side with the smaller spool diameter than onto the side with the greater spool diameter. Especially when driving the spool body by a friction roller, that drives the spool body conventionally at an ideal spot-like drive position realized by a spherically embodied friction roller coating, a constant rpm of the axle of the spool body will result. Without any additional features or devices, it is therefore impossible to attain a constant winding speed for all possible placement positions.
For winding devices driven by friction rollers, in which the yarn is supplied with a constant feed speed, it is known to store length of yarn in mechanical yarn storage devices, for example, pitching or take up levers. During the movement of the yarn guide from the side with the greater spool diameter to the side with the smaller diameter, yarn is introduced into the yarn storage device and is then released upon return movement. The control of such yarn storage devices is synchronized to the placement position such that the overlap of the movement laws of the spool body and the yarn storage device provide for a constant feed speed. Due to the different winding speeds at the smaller and the greater spool diameter, high yarn tensioning peaks would result without such yarn storage devices and would cause stretching or compression within the yarn and thus would increase the yarn breakage rate. With conventional conical spool designs, the yarn tension peaks are so high that, in practice, it is impossible to eliminate such storage devices.
For winding devices driven by friction rollers and with which yarn is removed, it is possible, in principle, to do away with such storage devices. Since, however, a constant removal speed cannot be achieved, the quality parameters of the yarn will change, for example, in twisting machines the twist along the placement direction. This is also undesirable.
In a winding device disclosed in German Offenlegungsschrift 24 58 853, the rpm of the spool body is synchronously changed with the movement, respectively, the respective instant placement position of the reciprocating yarn guide for conical, frictionally driven cross spools whereby, for driving the spool bodies, a plurality of rollers distributed axially along the spool length are employed which are driven synchronously and in sequence with the movement of the reciprocating yarn guide in order to wind the yarn with a substantially constant speed. The rollers which are axially arranged along the active length of the friction roller are then driven by a friction drive element coupled to the reciprocating yarn guide and accordingly moving in the longitudinal direction of the spool body in a reciprocating movement whereby the plurality of friction drive elements are driven by a single shaft for each machine, respectively machine side.
It is not disclosed whether the rollers distributed along the friction roller have spot-like drive positions by arranging thereat corresponding coatings. This would result in a discontinuous change of the winding speed. Due to the indirect drive of the rollers by the reciprocating friction drive element, it is, however, very likely that respective coatings are not provided. Accordingly, when supposing that ideal conical spools are used, torsion forces across the roller elements in the spool longitudinal direction will result. Independent of the presence or absence of such coatings, in any case, torsion forces will result because due to the final length of the friction drive element it is unavoidable that two rollers are simultaneously driven. These torsion forces will result in a high wear of the winding device and, in any case, will result in yarn damage of the respectively outer yarn layer of the spool body.
When considering the conical spools available in practice which are not ideal with regard to their conical design, slight saddle formations, i.e., oversized diameter increases at the spool flanks, may already make the basic principle questionable because the saddle formation will allow only a few rollers, in general, the two outer rollers, to drive the spool body. For a friction roller drive with a spot drive position, it is conventional to affect a modification of the placement angle resulting in a slight greater spool diameter increase at the drive point in order to thus eliminate the effect of saddle formations. This is, in principle, not possible in the suggested solution according to German Offenlegungsschrift 24 58 853 because the basic principle is to have a drive point which moves axially along the longitudinal spool direction.
The multi point support of the divided roller of the friction roller as well as the support of the continuous shaft supporting the friction drive elements which performs a translatory as well as a rotatory movement is complicated and thus cost-intensive. The suggested solution has many problems in regard to its operating principle.
It is therefore an object of the present invention to provide a method and a device with which in a simple manner problems for winding yarns onto a conical spool body, to which yarn is supplied with a constant speed or which supplies yarn at a constant speed, can be solved. The yarn winding action should be performed so as to be gentle to the yarn, i.e., torsion forces and yarn tension peaks are to prevented. The textile-technological properties, for example, the twist in the yarn or the twisted yarn should remain constant during the entire spool travel and especially independent of the placement position. Furthermore, the conventionally required mechanical yarn storage devices should be eliminated.